Mechanical energy cost and walking speed in elders

• Main Authors: Cheng-Chin Chuang, 莊政欽
• Other Authors: 章良渭
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/86194204294423774796

碩士 === 國立臺灣大學 === 醫學工程學研究所 === 101 === Background: While metabolic energy cost ambulation has been extensively investigated, mechanical energy cost is relatively unexplored which will be discussed . There were evidences to show that under the same walking speed the older consume higher metabolic energy than the younger. Research literatures also support that the self-selected walking speeds are not much different between the two groups but the cadence of the elders is higher. Furthermore, the aged group showed a redistribution of joint torques and powers during gaits. Purpose: The study is designed to answer the prominent research question: Would the redistribution of joint powers in elders change the segmental energy distribution and cause the high mechanical energy cost during level walking and how? Energy flow analysis would be conducted to look into biomechanical reasons that cause higher energy cost in elders. Materials and Methods : 15 male young (24.2 ± 0.77yrs) and 15 male older adults(71 ± 3.46yrs) participated in the study. Their anthropometric characteristics were: Young: Height (1.76 ± 0.02m), Mass (70 ± 9.37kg), BMI (22 ± 2.92). Elders: Height (1.64 ± 0.01m), Mass (65 ± 3.76kg), BMI (24 ± 1.28). All subjects walked along a 10-meter walkway with shoes at slower speed, self-selected speed and faster speed, respectively. There were 24 segmental landmarks tracked at 100 Hz by two optoelectric sensors (Optotrak Certus, Northern Digital Inc., Waterloo, Canada) for capturing body motions. The kinetic data will be synchronously collected via three force platforms (Accugait, Advanced Mechanical Technology Inc., Massachusetts, USA) embedded in the walkway. Each subject completed at least three successful gait trails after 3-minute practice. Results: For walking speed, it is not significantly different between young men group and elders group. However, a t-test analysis indicated a significant difference between the means of mechanical energy cost of the two groups. We focus on second double limb support(50%-62%), initial swing(62%-75), mid swing(75%-85%), and terminal swing(85%-100%). An independent t-test was conducted evaluated the means of potential and kinetic energy of the two groups. Especially during fast walking, the walking speed is not significantly different, and the segmental kinetic energy is also not significantly different. In analyzing the energy rate of segments and joints by discussing linear and angular flow individually. For linear energy flow of joints, the linear energy rate for proximal and distal are almost symmetrical to the x-axis, it means that the energy rate of the opposite ends of hip joint are with the same value but different signs. The physical meaning is that the linear energy flow is through the joint, but it does not appear on the overall joint power. Conclusions: The cost for fast walking is pretty higher in elders compared to it of young men. A partial explanation for this may lie in the fact that during walking, elders could not store energy effectively, so they change their strategy of walking and joints should generate additional power, and cause higher mechanical energy cost.